1. Field of the Invention
The present invention relates to a Schottky diode structure and a manufacturing method thereof, and more particularly to a Schottky diode structure based on metal/n-InP contact.
2. Description of the Prior Art
Owing to the surface Fermi level pinning arising from the presence of large surface states and other nonstoichiometric defects, the Schottky barrier height greater than 0.5 eV is very difficult to obtain on n-InP. Such a small barrier height causes a large reverse leakage current and hinders the development of inP device applications. A common approach to increase the Schottky barrier height is to form a thin dielectric layer between the metal and the n-InP substrate. Various techniques such as H.sub.2 -plasma or PH.sub.3 -plasma treatment, growing a thin P.sub.3 N.sub.5 film, PO.sub.x N.sub.y H.sub.z film, or an interfacial oxide layer on the InP surface were employed to treat the surface of InP to increase the Schottky barrier height. Schottky diodes fabricated by applying these techniques typically have a barrier height of about 0.7-0.8 eV. Recently, a low temperature (77K) deposition was reported for the metal/n-InP contact to obtained a Schottky barrier height as high as 0.96 eV [Z. Q. Shi, et. al., Appl. Phys. lett. 59, 446 (1991)]; however, it also has a shortcoming of large reverse leakage current. J. Dunn and G. B. Stringfellow in their article, entitled "Ag/Al Schottky Contacts on n-InP", Journal of Electronic Material 17, 181 ( 1988), disclose Ag/Al/n-InP Schottky diode which has a barrier height of only 0.65 eV. Moreover, the current voltage characteristics of this Ag/Al/n-InP Schottky diode is also not very satisfactory.
Therefore, there is a need in the industry to develop a new structure of Schottky diode having a relatively higher barrier height and a reduced reverse leakage current.